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volume of toxic material is less than 15% of the total volume of material to be <br />replaced, dilution of the toxic material can be successful. <br />Two primary concerns identified by the Division as a part of the PR-1 review were in <br />regard to potentially acid forming materials associated with the Lennox coal seam and <br />` excessive clay contents associated with shale strata overlying the Lennox. The <br />Division requested SCC to prepare a spoil sampling plan and mitigation plan for areas <br />where the Lennox would be spoiled, and for areas where the Lennox would potentially <br />be exposed by highwall reduction. A more detailed mitigation plan for areas of <br />excessive clay content was also requested. <br />SCC submitted an acceptable sampling plan to be employed in areas potentially <br />affected by Lennox spoil or outcrop within the original permit area. The same <br />sampling plan was to be applied to all regraded spoil areas and graded final highwalls <br />in the south extension mining block. The plan called for samples to be taken on 500 <br />foot centers within the designated area, and analyzed for clay content, pH, and <br />acid-base potential. Mitigation was to include additional sampling to define the area <br />of concern, deep ripping of areas of unsuitable clay content and amendment or burial <br />of acid forming material with a minimum of four feet of suitable material as cover. <br />The regraded areas were sampled during reclamation as required, and all of the <br />samples indicated nc mitigation would be required. <br />Nitrate-nitrogen levels were excessive in 14% of the overburden core samples taken at <br />the Seneca II-W Mine. The locations of the holes which exhibited elevated levels <br />were distant from one another. Furthermore, the stratigraphic locations of the elevated <br />nitrate-nitrogen samples are not correlative. Due to the vertical and horizontal <br />distances between locations containing elevated nitrate-nitrogen levels, percolating <br />ground water will not be adversely affected. The dilutional effects of a predicted <br />spoils aquifer should buffer the concentration of nitrate as nitrogen by the time the <br />aquifer discharges to the surface system. <br />Wolf Creek/Sage Creek Overburden/Underburden Assessment <br />Only two parameters (iron and lead) exhibited unsuitable levels within sampled <br />increments from the one bore hole that penetrated the sequence in the south extension <br />area. Within each of four delineated intervals (Sage Creek overburden, Upper Wolf <br />Creek overburden, Lower Wolf Creek overburden, and Wolf Creek underburden), <br />composite samples were taken from each 10 foot depth increment. The average value <br />for lead within the Lower Wolf Creek overburden interval was in the unsuitable range, <br />due to a very high value within one of five sampled increments. One or more sample <br />increments within the Sage Creek and Wolf Creek overburden intervals exhibited <br />unsuitable iron levels, but the average iron level within each interval was suitable. <br />One of six sampled increments in the Upper Wolf Creek overburden was in the <br />unsuitable range for lead, but the average value for the interval was marginally <br />Seneca II-W Findings Document 26 C1982057 <br />Permit Renewal No. 5 December 9, 2010